Pulp storage tank current control



Dec. 8, 1953 E. J. GRUEN 2,661,668

PULP STORAGE TANK CURRENT CONTROL 'Filed March 18, 1950 2 Sheets-Sheet 1I s l //v VENTOR Q 5. J. GRUE/V C A TTOPNEV Patented Dec. 8, 1953 1UNITED I STATES PATENT-OFFICE a, 2 1,668" I I T PULP STORAGE TANKCURRENT c'oNrRoL Ernest J. Gruen, Carteret, N. .L, assignor to WesternElectric Company, Incorporated, New York',=

N. Y., a corporation of New York I v Application March 18, 1950, seams.150,446 I ZClaim's. (01. 92-37) 1 This invention relates to themanufacture of paper pulp and particularly to preventing pulp fromsettling out of suspension in storage tanks. Paper pulp as generallyused in the paper making industry and also in the insulation ofelectrical conductors is usually procured in sheet form, the sheetsbeing fed through apparatus for breaking the pulp into small particles.After the pulp particles have been reduced to the proper size, they areimmersed ina Water conveyor, and the pulp suspension passed throughbeating machines, which impart work to the fibers and increase theslowness of the pulp to give to it desired physical properties such astensile strength.

From the beating machines, the pulp suspension .is pumped into a tank,which stores the suspension until thewire insulating machines are readyfor the pulp. In passing from the storage tanks to the insulatingmachines, the pulp slurry is passed through Jordan machines which exerta cutting action on the pulp fibers, after which sufficient water isadded to the slurry to bring the consistency of the suspension to thefinal desired value.

While the pulp is in suspension in the storage tank, it is necessary tokeep the slurry in a state of agitation to prevent the pulp fromsettling out of the suspension and to prevent lumping of the pulp whichremains in suspension. Either of these results would cause-unevendistribution provide one or more propeller mixers to impart velocity tothe pulp suspensionin conjunction with a centrally located plate ormidfeather which serves to increase the velocitythus created.

It has been found that while this method has been generallysatisfactory, there has been a tendency for dead pockets of pulp slurryto form on the backside of the midfeather because of the velocity of theslurry as it passes around the end of the midfeather. These dead pocketsare undesirable as they allow part of the pulp in the storage tank toeither settle out or form lumps which cause poor insulation to be formedon the Wires. Attempts to eliminate these dead pockets by running theagitating mixers at slower speeds have not proved to be an adequatesolution as the resultant lower velocity of the slurry increases thetendency of the pulp to settle out from the suspension as a whole.

It is therefore an object of this invention to eliminate the dead.pockets which are formed duction-boxes l5.

when this conventional method of agitating pulp slurry in the storagetank is used.

Applicant accomplishes'this' object according to the invention byproviding the midfeather with a plurality of openings which allowsuilicient slurry to pass throughthe plate to prevent the formation ofthesepockets.

' Other objectsand features will be apparent from the following detaileddescription taken in conjunction with the attached drawings in which:

Fig. 1 15a plan view of the storage tank, including the agitator pumpdrives;

Fig. 2 is a side elevational view of the tank, partly in section,showing the location of the openings in the central plate;

Fig. 3 is a sectional view of oneof the openings in the central plate,taken along the line 3-3 ofFig.2

With re'ference'to the drawings, the tank used for the storageof thepulp suspension is designated as II. In installations where the paperinsulation of electrical conductors takes place on an extensive scale,tanks'of this type often become quite large insize, having dimensions ofthe order of 36" long by 18' wide by 8 high. The

pension fromthe tank to the Jordan machines in preparation'for being fedinto the insulating machines.

Mixer motors are used to provide agitation for the pulp suspension: inthe storage tank. These motors are mounted on bases 13 and havepropeller shafts l4 driven from suitable gear re- These shafts M aresupported by housings l6v at the points where they enter the end wallof, the storage tank H and are supwithin the interior of the tank fromthe main tank wall as shown in Fig. 1. The supporting wall l8 has twoopenings !9 which allow the pulp slurry to pass through the Wall as itis drawn by propellers 20 mounted on the ends of shafts l4.

As the pulp slurry is forced through the openings I9, it continues onaround the oblong shaped tank, as shown by the arrows, passing in itstravel up one side and down the other of a vertical plate or midfeather25. This midfeather, which is approximately as high as the tank, extendsfrom the interior end of the'support'ing Wall [8 to a point only a fewfeet, from the opposite end wall of the tank. As will be seen from Fig,1,

the midfeather is slightly offset from the longitudinal axis of the tankso that the channel on one side is narrower than on the other. Thiscauses an increase in velocity and head of the Slurry flow in thenarrower channel, and results in a difference in the solution level inthe two sides.

When the pulp slurry is kept moving by the propeller mixers at a ratefast enough to prevent settling of the pulp from its water conveyor, thevelocity of the slurry around the end 26 of the midfeather often createsundesirable pockets in the suspension in the vicinity marked Applicanthas discovered that by creating openings 2': in the midfeather adjacentto this area, the difierence in liquid level on the two sides will causea certain amount of slurry to pass through these openings in thedirection shown instead of going around the end 26 of the midfeather,the slurry thu passing through being sufficient in quantity and having avelocitygreat enough to prevent the formation of these dead pockets.Uniform distribution and consistency of the pulp when it is pumped tothe wire insulating machines is thus assured.

It has been found that when the pulp suspension in the tank has reacheda-sufiiciently low depth, the mixers l2 would have sufficient powerwithrespect to the volume of slurry in the tank to move the slurry at avelocity high enough to create a back-eddy current in the area where thedead pockets normally occur. The cost of agitating equipment largeenough to create preventive back-eddy currents of this type when thestorage tank is full would be prohibitive, and good economic practicedictates the use of mixers which would have power sufficient to createsuch eddy currents when the pulp suspension is from one-third toone-half full tank level. The

openings 21, which have been formed in the mid' feather, are thereforelocated in the upper half of the midfeather so as to prevent theformation of dead pockets from a full level of pulp slurry down to alevel at which the mixers are sufliciently strong to prevent theirformation.

The openings 21 are approximately 6" high by 18" long for large storagetanks of a size as previously noted. As seen in Fig. 3, the bottom ofthese openings are sloped downwardly approximately from the highpressure side to the low pressure side so that the pulp will flow offafter the liquid level has gone below the opening. The spacing of theseopenings as shown in Fig. 2 has proved satisfactory in actual prac tice,this arrangement comprising three openings in an upper level and twoalternately spaced openings in a lower level.

The openings 2'! should be made small enough in size with respect to thesize of the storage tank to prevent their acting as a by-pass of thenormal slurry flow, and thereby creating possi ble dead pockets at theend of the storage tank adjacent the end 26 of the midfeather.

' there exists the problem of preventing a subdead stance from settlingout of solution while in storage.

It is to be understood that the above described arrangements are simplyillustrative of the application of the principle of the invention. Nu-

merous other arrangements may be readily devised by those skilled in theart which will embody the principles of the invention and fall withinthe spirit and scope thereof.

, What is claimed is:

1. A horizontally oblong storage tank for pulp slurry having amid'feather wall extending longitudinally of the tank and terminatingshort of the ends thereof means disposed within and adjacent the bottomof the tank near one end or the wall for causing "the slurry tocirculate in a circuitous path around the near and 'far ends of the wallat a rate sufii'ci'ent to maintain the pulp in dispersed suspensionwhenfthe level of the slurry in the tank is at an intermediate level,said means being insufficient to prevent the formation of dead pocketsadjacent the far end when the slurry is at high levels in the tank, saidwall having a plurality of spaced apertures disposed in a group in itsupper portion adjacent its far end to prevent the formation of deadpockets when the slurry is at high levels in the tank.

2. A tank according to the preceding claim in which the midfeather wallis of substantial thickness and the apertures are located 'on at leasttwo levels and have sill sloping downwardly in the direction of slurrynow to prevent the pulp from lodging on the sills.

ERNEST J. GRUEN.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 1,277,637 Parkington Sept. 3, 1918 1,716,293 BO nd1;.......'.-..'. June 4, 1929 2,055,143 Bond s- Sept. 22, 1935 2,087,015B'Ofid July 13, 1937 2,270,847 Hyman Jan. 27, 1942 2,277,477 CrawfordMar. '24, 1942 2,452,399 Stadler Oct. 26, 1948 FOREIGN PATENTS NumberCountry Date

